Solvent extraction of synthetic latices



Patented Dec. 18, 1945 a i I ram OFFICE Albert M. cum-s, Stow, Ohio, and Charles F. Winans, Edgewood, Pa., assignora to Wingfoot Corporation, Akron, Ohio, a corporation of Delaware No Drawing. Application m 12, ms, Serial No. 442,622

3 Claims. (Cl. 2643-84) This invention relates to the solvent extrac= 1y high to permit satisfactory extraction. The tion of synthetic latices and, more particularly, heavy solvents, such as nitrobenzene, dichlorto the recovery of unreacted acrylic nitriles from benzene, brombenzene, dichlorethylether and emulsioncopolymerizationreactionsinwhichmore acetylene tetrachloride, etc. are somewhat exof such acrylic nitrile is present than copolymer- 5 pensive but are excellent solvents and suited for izes with the other monomer or monomers present. use in this process. The preferred solvents, how- It is not unusual to have excess acrylic nitrile ever, are ethers of eight to ten carbon atoms, present when copolymerization is effected with such as dibutyl ether and diamyl ether, butylamyl vinyl chloride, vinylidene chloride, styrene or a ether, propylhexyl ether, etc. butadiene' monomer such as 1,3-butadiene, iso w The copolymer may be formed, for example, by prene, 2,3-dimethyl butadiene, z-chloro-butadiene mixing the following materials:

or the like. Stopping the reaction before all of Parts by weight the acrylic nitrile has entered into the co- Butadlene 4 polymerization may in some cases give proper- Acrylic nitril 4 ties of the synthetic rubber produced, which may Emulsifier 10 be desirable. Sodium perborate 0.06 According to this invention, the acrylic nitrile Carbon tetrachloride 0.23 remaining after such partial copolymerization is Acetaldehyde in 0.22 parts by wt. recovered from the resultant latex by solvent exof water 0.0201

traction. Dibutyi ether and 'dlamyl ether have Potassium cyanide in 0.22 parts by wt.

:fen fgund to be the most satisfactory solvents of water 0.0092

use or the extraction.

According to this invention. the latex contam 103g; lfirgnulsitler may, for examplacomprise the ing thamunreacted acrylic nitrile is treated one or a Parts by weight more as w th the extractant and the extract 5 is separated from the latex by centrifuging. The 3 2 (sodium sulfate latex is the partially prepared uncoagulated mso'dmm phosphate, 0'07 product of emulsion type copolymerizatlon. some water N3 of the solvent is present in the water serum and I PM i Present in the latex particles, Th Instead of acrylic nitrile, any other of the acrylv m; u t t acrylic m-n 1 both the ic nitriles may be used in the above formula, such solid and u um phm, as ethacrylonitrile, methacrylonitrile, etc.

The solvent used must have ahigh solvent power such e mixture may be Pissed in e Bless lined tor the acrylic nitrile. It mustbeimmiscible with euweleve and run until the reeeflen 18 r water in order that separation may be eflected by simple ebOut 50% P Tms may centrifuging. h mm density dmerence about 2-3 hours at a temperature of about 32 between the solvent and the water the more efll- M the end 01 this time. the l x is pref rcient is the subsequent centrifugal separation of ably stabilized es for eXemPle y add ns an emulthe phases. Furth rmor fin greate the m. slon of benzene and phenyl beta naphthyl-amine fgr n b t n th b m point of the solvent in water or by adding an emulsion of the conand th particular u mm t more mdensation product of cresol and aniline. when clently th o nt n t acrync man may be the autoclave is opened, the unchanged or residseparated. The solvent must of course be chemiue1 buliediene w e pe s a gas and c n be cally inert t th materials t which is readily recoveredincomparative purity by known brought 1;; t t, t t have not more than means, but the unchanged acrylic nitrile remains a small or low tend to form stable emulin the latex, a part being dissolved or emulsified lo g, It u t b du enable and cheap in the water serum and a part being dissolved or Th aro a hydrocarbons such as toluene, yadsorbed by the particles of the copoiymer.

lene, tetralin, etc. are'quite easily emulsified and The solvent extraction may be carried out in som d not; hav t density diflerenge from various ways. It is preferably a multiple extracwater. They are, therefore, not altogether un;- tion or an extraction, effected on a counter-cured fo use in this process, In th cage of thehlgh rent basis. The extraction may be effected by boiling petroleum distillates the distribution coshaking the solvent with the latex or by sprayemeients of the acrylic nitriles between the pem a stream of fine particles of the latex down trui m d t aqueous phase e t v 111mm. 66- through lighter extraction media or up through ployed.

heavier extraction media. Any of" the various known means of blinding a solvent into contact 7 with a dispersion may be used.

After the extraction the solvent is separated from the latex by centrifuging. The centrifuging should be done at high speeds. for example, at a speed suillcient to give the eilect of about 6,000 times that of gravity or greater. Unless some vapor-tight equipment is employed, there may be a considerable loss of solvent due to evaporation as the liquid is thrown out from the discharge orifices of the rotor. The latex must be added to the centrifuge with care to keep coagulation lossestoaminimum. 1

- In carrying out the extraction the latex may be treated with half its volume of solvent or any other feasible proportion of solvent may be em- The solvent may become emulsified due to the presence of the emulsifying agent in the 7 thetic latex produced by a co-polymerization process which utilizes only a part of the acrylic nitrile present in the polymerization formula which comprises extracting the latex with an alkyl ether v aeohaa'r latex the; ether and the acrylic nitrile dissolved therein by subjecting the mixture containing the latex to separation in a centrifuge giving the effect of at least 5000 times thatof gravity.

2. The method of extracting an unreacted acrylic nitrile' from an emulsifier-containing synthetic latex produced by a co-polymerization process which utilises only a part of the acrylic nitrile present in the copolymerization formula which comprises extracting the latex with dibutyl ether. thereby dissolving acrylic nitrile in the ether, and then separating from the latex the ether and the acrylic nitrile dissolved therein by subjecting the mixture containing the latex to separation in a'centrifuge giving the efl'ect or at least 5000 times that of gravity.

3. The method of extracting an unreacted acrylicnitrlle from an emulsiiler-containing'synthetic latex produced by a copolymerization process which utilizes only a part of the acrylic nitrile present in the polymerization formula which comprises extracting the latex with diamyl ether,

thereby. dissolving acrylic nitrile in the ether;

and then separating from the latex the ether and the acrylic nitrlle dissolved therein by subjecting the mixture containing the latex-to separation in a centrifuge giving the effect of at least 5000 times that of gravity.

, ALBERT M. CLIFFORD.

CHARLES l WINANB. 

